Is it legitimate to break a conflict in the following way, when the alternative is to make a heading non-unique?

already established heading:

Kohen, Mosheh

(known to be the son of Hayim Kohen)

newly established heading:

Kohen, Mosheh$q(Mosheh ben David)

when the justification for the qualifier is an introduction where David Kohen refers to the author as "my son [beni, in Hebrew] Mosheh."

The forms "Mosheh ben David Kohen" or "Mosheh ben David" without surname don't occur anywhere.

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The answer from CPSO was: "No, I don't think we can make up a $q like that."